1. Field of the Invention
The present invention relates to an exposure apparatus which uses synchrotron radiation for, for example, manufacturing devices.
2. Description of the Related Art
An X-ray exposure apparatus has been proposed in which a mask pattern is transferred onto a wafer in close proximity thereto by exposure using X-rays as illumination light in the manufacture of semiconductor integrated circuits having a high degree of integration.
In the manufacture of semiconductor integrated circuits, the exposure process is performed in a plurality of lines in order to increase the productivity, and a plurality of the same X-ray masks are prepared. The pattern to be formed on a mask is generally formed by a method of drawing by an electron beam drawing apparatus. However, the time required for drawing a circuit pattern having a degree of integration on a 256 Mbit-DRAM scale is several minutes, and sometimes reaches several hours, and much time is thus required for forming a plurality of masks.
On the other hand, there is known a method of duplicating an original pattern by proximity X-ray exposure, or life-size exposure, using an original mask formed by the electron beam drawing apparatus to form a plurality of X-ray masks. The X-ray exposure apparatus can employ a wide exposure region, and exhibits a shorter time required for exposure than that in electron beam drawing. Thus, this method can significantly improve the productivity of masks.
In order to absorb X-rays, an absorber pattern made of gold or the like and having a thickness of about 0.7 .mu.m is formed on the X-ray mask by plating or etching. Although the electron beam drawing method uses a multi-layer photosensitive material for obtaining a thick absorber layer, the proximity X-ray exposure method can expose a photosensitive material having a sufficient thickness because a resolvable depth is large, and can employ the exposure process using a single layer of photosensitive material. The X-ray exposure method can therefore sometimes form X-ray masks at a cost lower than that in the electron beam drawing method.
Considering the above advantageous conditions, attention is paid to the method of forming X-ray masks for wafer exposure by using the X-ray exposure apparatus.